Axial flow fan or pump



June l5, 1937. F. scHlCHT y AXIAL FLow FAN on PUMP Fild March 3l, 1954 /NVE'NTO/G Patented June 15, 1937 mit? I application March 3l, lg3d, Serial No. li in Geany May 5, 1933 5 Staines. A(Ci. ZSiPmllZii) This invention relates to axial ow fans or pumps and particularly to rotary fans or pumps by means of which pressuresv of the same order of magnitude may be obtained as with centrifu- 5 gal fans and pumps. The structural arrangement of pumps is similar to that of fans, and in the following description reference will be made only to fans to which the invention is particularly applicable.

l0 An object of this invention is substantially to reduce the `Weight and dimensions of a. fan or pump as compared with the weightand dimensions of the usual centrifugal fans or pumps, this feature being of particular importance when 15 large quantities of fluid must be delivered.

Another object of this invention is to provide a new fan or pump which with the same pee rlpheral velocity of the blade-carrying rotor as in the usual axial fans, will produce pressures of the order of 391/2 inches of water column, i. e., many times greater than they usual axial fans.

Another object of this invention is to provide a new fan or pump which will be silent in 25 operation and simple in manufacture.

' Another object of this invention is to provide a new fan or pump wherein the required energy will attain its maximum value in the neighborhood of the highest eciency of the fan and will 30 be somewhat reduced bythrottling and when a full quantity of uid is propelled.

These objects are attained by so shaping the surfaces of the rotor wheel hub, the annulus surrounding it, and the surfaces of the blades,

` 35 that the forces* which the rotor Wheel-exerts on the fluid to be conveyed increase only the speed at normal load without any change of pressure. I have found that a high degree of .eiciency can be attained only if this condition is exactly fulfilled. in all cross-.sections of the rotor wheel.

This is the case when a definite relation is established between the tangent led to each rotor blade and the corresponding cross-section of the rotor channel or passageD i2, F02) C I'get the angular coeilcient of a tangent led to the blades tgain the section considered at a radius from the following equation:

2 aga= z C Y z'imcz These equations may be applied to the case when the velocity of the fluid owing in a direction parallel to the axis is constant at all points of the entrance cross-sectional'area. If, however. for any reason the entrance velocity and direction differ, this circumstance must be taken into consideration when computing. In this case the channel of the rotor must be divided e. g., into an arbitrary number of thin annular channels, and we may assume that the conditions, in every-one of said individual channels are identical. If the entrance velocity is not parallel to the axis, the pitch at theV inlet must be correspondingly changed and the respective angular change must be maintained throughout the blade up to the outlet.;

Such a design represents a preferred embodiment, but small deviations therefrom (Within a range of to 20 percentum) have no appreciable eilect, since within said range of deviations the flowing fluid remains generally in contact with'the blades.V The greater the deviation, the narrower the efficient working range of the fan.,

I iS F1.

One may first determine either the shape of the blades or the cross-sectional area or shape of the channel, whereupon the cross-sectional area of the channel or theshape of the blade may be computed.

, 'I'he appended drawing shows both possibilities in a largely diagrammatic manner.

The invention is illustrated in the annexed drawing in two embodiments.

Figs. 1 and 2 are axial sections through the blowers; y

Figs. 3 and 4 show curves along which six cylindrical surfaces coaxial with the axis of the rotor and at distances r1 to re intersect the surface of the rotor blades;

Figs. --12- are sections' through the blades along the above-mentioned.cylindrical s urfaces, the sections being developed into a plane.

In the form of construction shown in Fig. 1 the axial section through the rotor conduit has been so selected that the two limiting surfaces thereof are formed by conical surfaces which are arranged at such a distance one from the other that on the inlet side of the conduit there appears an annular surface the area of which is Fo. Fi is a radial plane which intersects the conduit in an annular surface the area of which Fig. l shows further in dotted lines six intersections in which six cylindrical surfaces R1, R2, R3, R4, R5, Re which are coaxial with the axis of the rotor and the respective radii of which are r1, r2, r3, r4, 15, vn; intersect a vertical plane passing through the axis of the rotor. The said cylindrical surfaces Ri-Re intersect the surface of the rotor blades'in curves Ai-As shown'in Fig. 3 in which the `cylindrical surfaces Ri-Ra as well as the curves Ai-Ae are shown developed into a plane.

The tangents ledin any desired point to the said curves should form with the axial direction an angle a the function tga of which conforms to the above-mentioned equation. Fig. 3 showsl for instance, the tangents Ti 'and .T4 led in points'ai and a4 to the lines A1 and A4, respectively, which form with the axial direction angles a1 and au.' respectively. The point a1 lies on the cylindrical.,

surface A1 and the point a4 lies on the cylindrical surface A4, the two points being positioned on the same radial surface Fi.

Alli values appearing in the above-mentioned equation for tga either are given beforehand or may be measured on the'selected section of the conduit. It is possible, therefore, to calculate the angles a for any desired number of points lying in any predetermined cross-section, for instance, Fi, and this calculation may be repeated 4 for any desired number of radial cross-sections through the conduit. Then by interpolation it is possible to-determine by this method the shape I measured directly, and the abov'e'mentioned equation for tgm permits the computation of the area of a number of radial cross-sections of the rotor conduit and thus the design of the shapeA of the conduit.

aos-1,1 1 1 and vice versa; there is no limitation as to the choice of one or another of these elements. The

smaller the ratio of the exit sectional 'area to that of the entrance, the greater will be the increase in fan pressure. i

A guiding apparatus L (Fig. 2) adjacent rotor R checks the whirling movement of the helical flow. VSince the exit velocity is very high, a conventional conical diffuser D is preferably arranged behind the fan, said diffuser transforming velocity into pressure.

Referring to Figures 1 and 2 in detail, I denotes the rotor and 2 the blades. The hub of the rotor is designated 3 and the surfaces of the hub are denoted 4. 5 designates the surrounding annulus and F1 the annular surface. The wheel axle is designated 6, and 1 denotes the guiding apparatus. 8 denotes the diiusor and I0 the limiting walls of the rotor channel in Figure 1, and Il denotes'the limiting walls of the rotor channel in Figure 2.

What I claim is:

1. In an axial flow rotary fan or pump for propelling fluids, a rotor having blades and a hub, the surfaces of the rotor Ihub and of the surrounding annulus and the4 surfaces of the blades being so shaped that a tangent led at any point to theY curved line along which any cylindrical surface coaxial with the axis of the rotor intersects the surface of the blade bears the following relation to an annular surface corresponding to a section through the hub and the outer annulus and through the tangent point and normal to the wheel axis: e

whereby theforces which the rotor exerts on the uld to be conveyed cause at normal load only an increase of speed without any change of pres-- Sure.

2. In an axial flow rotary fan or pump for the propelling of gases or liquids, the combination with rotor blades driving the fluid, of a guiding apparatus checking the whirl movement of the "helical iiow from the rotor, and of a diiusor transforming the velocity acquired in the rotor into pressure, sai-d rotor blades having a definite shape such that their sections with a cylindrical surface coaxial with the rotor axis stand in a definite mathematical relation to the area of the corresponding section of the rotor channel, said mathematical relation being expressed bythe following equation 3. In an axial flow rotary fan or pump for the propelling of gases or liq'uids, the combination with rotor blades driving the fluid, of a guiding apparatus checking the whirl movement of the helical flow from the rotor, and of a diffuser transforming the velocity acquired in the rotor 'into pressure,the limiting walls of the rotor channel representing converging conical surfaces providing a rapid narrowing of the initial portion of fthe rotor channel and thereafter but a slight di- 4. In an axial flow rotary fan or pump for the propelling of gases or liquids, the combination with rotor blades driving the fluid, of a guiding shape of said rotor blades being such that the tangents led to a developed cylindrical section of a blade stand in a denite mathematical relation to the area of the corresponding section of the rotor channel, said mathematical relation being expressed by the following equation:

5. In an axial flow rotary fan or pump for the propelling of gases or liquids, the combinationA with rotor blades driving the fluid, of a guiding apparatus checking the whirl movement of the helical ow from the rotor and of a diiusor transforming the velocity acquired in the rotor into pressure the limiting walls of the rotor -ch'annel representing converging conical surfaces providing a rapid narrowing of the initial portion of the rotor channel and thereafter but a slight diminishing of its cross-sectional area, said rotor blades being of such a shape that any'tangent led to a section of the rotor blade, which section is developed by a cylindrical surface coaxial with the rotor shaft, is related to the respective sec tional area of the rotor channel by the following equation:

wherein Q :quantity of air,

w :angular velocity,

Fo=cross sectional area. of an annulus at the entrance of the channel, F

considered section of the channel, r :radius of a. co-axial cylindrical surface intersecting the blades.

FRIEDRICH SCHICHT.

:cross sectional area of an annulus of the 

